1. Field of the Invention
The invention relates to a display method and an illumination system thereof, and more particularly to a display method and an illumination system which increases light usage.
2. Description of the Related Art
FIG. 1 shows an illumination system of a conventional projection device, wherein a plurality of spot light sources 11, 12 and 13 provide a first light beam (blue) 1, a second light beam (green) 2 and a third light beam (red) 3. The first light beam (blue) 1, the second light beam (green) 2 and the third light beam (red) 3 pass a scrolling element 14 to be scanned on a light valve 15 and mixed into white light beams. With reference to FIGS. 2a, 2b, 2c and 2d, the first light beam (blue) 1, the second light beam (green) 2 and the third light beam (red) 3 are spot light beams, and energy distributions thereof are in Gaussian distribution. Therefore, when the first light beam (blue) 1, the second light beam (green) 2 and the third light beam (red) 3 pass the scrolling element 14 to the light valve 15, decreased area of light spots are utilized, and serious light overfill is generated. As shown in FIG. 2d, a first overfill area 1′ surrounds the first light beam 1, a second overfill area 2′ surrounds the second light beam 2, and a third overfill area 3′ surrounds the third light beam 3. With reference to FIGS. 2a and 2d, only part of the first light beam 1, the second light beam 2 and the third light beam 3 pass the light valve 15 to be used, and areas between the light beams (space areas and overfill areas) are defined as spokes 4 which are stopped by the light valve 15. Conventionally, square measure of spoke 4 is large, and light usage is thus decreased.